This application claims priority under 35 U.S.C. xc2xa7xc2xa7119 and/or 365 to Ser. No. 98-30376 filed in Korea on Jul. 28. 1998; the entire content of which is hereby incorporated by reference.
1. Field of the Invention
The present invention relates to a differential spiral magnetic field sensing device having microscopic closed magnetic paths integrated on a semiconductor substrate with a signal processor, and a magnetic field detection module, and more particularly, to a differential spiral magnetic field sensing device for detecting a magnetic field weaker than a terrestrial magnetic field using a soft magnetic film core, and a magnetic field detection module which is integrated on a semiconductor substrate with a signal processor by applying a LIGA (Lithography, Galvanoforming, and plastic molding)-like technique and an IC (Integrated Circuit) fabrication technique to the differential spiral magnetic field sensing device.
2. Description of the Related Art
A magnetic sensor using a soft magnetic material and a coil has long been used as a magnetic sensor with high sensitivity. Such a magnetic sensor is manufactured by winding a coil around a relatively large rod-shaped core or an annular core made of soft magnetic ribbon. In order to accurately detect a magnetic field, an electromagnetic circuit is necessary. A method in which a magnetic field sensing element of the magnetic sensor is attained by a soft magnetic film core and a planar film coil has been proposed.
As shown in FIG. 1, a conventional weak magnetic field sensing device is manufactured using soft magnetic film cores 1a and 1b and a planar film coil. These two cores 1a and 1b are arranged in parallel in the direction of a detection axis to then be differentially driven. This is for offsetting an induced voltage based on electromagnetic induction when no external magnetic field is applied such that an excitation coil 2a-2b and a magnetic field detecting coil 3a-3b are wound around two soft magnetic film cores 1a and 1b. Thus, the conventional weak magnetic field sensing device requires a large area. Also, due to a magnetic flux variation generated by the excitation coil 2a-2b and a magnetic field detected by the magnetic flux variation detecting coil 3a-3b, leakage of magnetic flux through the soft magnetic film cores 1a and 1b cannot be avoided, which makes it difficult to detect a magnetic field with high sensitivity.
Since the conventional weak magnetic field sensing device is manufactured by winding a coil around a relatively large rod-shaped core or an annular core made of soft magnetic ribbon, the manufacturing cost thereof is high.
To solve the above problems, it is an objective of the present invention to provide a differential spiral magnetic field sensing device with a high sensitivity, which can accurately detect an external magnetic field, and can be fabricated on a microscopic scale on a semiconductor substrate, and a magnetic field detection module using the same.
Accordingly, to achieve the above objective, there is provided a differential spiral magnetic field sensing device including a semiconductor substrate, soft magnetic film cores stacked on the semiconductor substrate to be laminated to form closed magnetic paths, an excitation coil formed of a metal thin film for alternate excitation of the soft magnetic film cores, a magnetic flux variation detecting coil made of a metal thin film for detection of magnetic flux variation in the soft magnetic film cores, and a zero magnetic field detecting coil for generating anti-magnetic field components for eliminating magnetic flux variation in the soft magnetic film cores generated by an external magnetic field.
In the present invention, the soft magnetic film cores are preferably divided into two parts to then be arranged parallel to each other, the two-part soft magnetic film cores are sub-divided into a predetermined number of parts, the excitation coil is wound n turns, where n is a positive integer, the magnetic flux variation detecting coil is wound m turns, where m is a positive integer different from n, and the zero magnetic field detecting coil is wound one turn, the excitation coil, the magnetic flux variation detecting coil and the zero magnetic field detecting coil being laminated, and wherein when an external magnetic field is zero, the induced waveforms caused by the excitation coil are offset. Also, two soft magnetic film cores are arranged one on top of the other, and the excitation coil, the magnetic flux variation detecting coil and the zero magnetic field detecting coil are laminated on three planes in the form of spiral bottom-layer, middle-layer and top-layer wires between the soft magnetic film cores.
Also, according to another aspect of the present invention, there is provided a magnetic field detection module including a differential spiral magnetic field sensing device having a semiconductor substrate, soft magnetic film cores stacked on the semiconductor substrate to be laminated to form closed magnetic paths, an excitation coil formed of a metal thin film for alternate excitation of the soft magnetic film cores, a magnetic flux variation detecting coil made of a metal thin film for detection of magnetic flux variation in the soft magnetic film cores, and a zero magnetic field detecting coil for generating anti-magnetic field components for eliminating magnetic flux variation in the soft magnetic film cores generated by an external magnetic field, an excitation coil driving circuit connected to the excitation coil and integrated on the semiconductor substrate, a magnetic field detecting signal processing circuit connected to the magnetic field variation detecting coil and integrated on the semiconductor substrate, and a zero magnetic detecting signal processing circuit connected to the zero magnetic field detecting coil and integrated on the semiconductor substrate.
In the present invention, preferably, the soft magnetic film cores are divided into two parts to then be arranged parallel to each other, the two-part soft magnetic film cores are sub-divided into a predetermined number of parts, the excitation coil is wound n turns, where n is a positive integer, the magnetic flux variation detecting coil is wound m turns, where m is a positive integer, and the zero magnetic field detecting coil is wound one turn, the excitation coil, the magnetic flux variation detecting coil and the zero magnetic field detecting coil being laminated, and wherein when an external magnetic field is zero, the induced waveforms caused by the excitation coil are offset. Also, two soft magnetic film cores are preferably arranged one on top of the other, and the excitation coil, the magnetic flux variation detecting coil and the zero magnetic field detecting coil are laminated on three planes in the form of spiral bottom-layer, middle-layer and top-layer wires in the soft magnetic film cores. Further, it is preferable that the excitation coil driving circuit includes a rectangular wave oscillator for generating rectangular wave voltage pulses, a frequency divider for dividing the rectangular wave voltage pulses to a half and a fourth, respectively, a waveform converter for converting the one fourth rectangular wave voltage pulse into a triangular voltage pulse, and an excitation coil driver for driving the excitation coil using the triangular voltage pulse.